The twin that Hanna's mother sees in this episode is the twin that did the stabbing in Alison's story in season 2's Halloween episode, identifiable by the birthmark on her right cheek.
Original International Air Dates:
Canada: October 23, 2012 on MuchMusic
The Lady Vanishes
In one scene, someone asks Aria her name but cannot hear her answer because of a noise, so she writes it on the fogged window of the train, then subsequently goes missing. These plot points are all from the Hitchcock film The Lady Vanishes.